Valtteri Bottas spearheaded a straightforward Mercedes one-two in the first practice session for the Russian Grand Prix at the Sochi Autodrom.
Mercedes head into this weekend as favourites as it has won all seven grands prix at the circuit since it made its debut in 2014, with Lewis Hamilton taking the chequered flag on four occasions, Bottas twice - including last year - and Nico Rosberg the other.
The team, however, is enduring its leanest run in F1 in the current turbo-hybrid era as it has won only one of the last 10 races, although still holds an 18-point lead over Red Bull in the constructors' championship.
In a dry hour-long run - given heavy rain is forecast throughout Saturday - on one of his favourite circuits given its predominantly front-limited nature, Bottas posted a lap of one minute 34.427secs, finishing 0.211s clear of Hamilton.
Championship leader Max Verstappen, on a second soft-tyre run as he was over seven-tenths of a second adrift on his first, managed to close the gap to 0.227s to Bottas at the close.
The Red Bull driver knows he ideally needs to be as close to the front as possible this weekend to negate a three-place grid penalty he will serve on Sunday as punishment for the collision he caused with Hamilton at the recent Italian Grand Prix.
Charles Leclerc, with his SF21 sporting a new power unit incorporating an updated hybrid system that means he will start at the back of the grid on Sunday, fared well as the Monégasque was fourth quickest.
Leclerc finished 0.690s down on Bottas and was the only other driver to finish within a second of the Finn, with Aston Martin's Sebastian Vettel 1.354s off the pace in fifth on the timesheet.
AlphaTauri's Pierre Gasly was just 0.013s behind Vettel, with Carlos Sainz a further 0.017s down in an 'older' Ferrari as only Leclerc is running the new system across the weekend.
McLaren's Lando Norris, who endured the only moment of concern in a quiet session when he ran off track at turn 10, finished 1.532s back in eighth place, and nine-tenths clear of 14th-placed team-mate Daniel Ricciardo, fresh from his Italian GP triumph.
Norris also later bizarrely lost the rear of his car in the pit lane entry slip road as the session had finished, sliding and clipping the wall, damaging his front wing.
Red Bull's Sergio Perez and Alpine's Lando Norris completed the top 10, the latter followed by team-mate Esteban Ocon, the Frenchman the last of those to be within two seconds of Bottas.
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